new user

I'm a new user hear and just need so help. I have 1979 firebird formula. Its has a 383 stroker motor in it and many other race good. About a year ago I took the frount subframe out to clean it and replace the rubber mounts with soild alumiunm mounts. Well all went well but I don't have a lift so I just laid under it. Well I put the stroker in it after that and it ran fine but at about 3500rpms the can would vibrate so I replaced the u-joints and had the drive shaft checked to see if it was bent. This did not work so I reboiult the 4 speed because I tought the center bearing went out this did not work. Well I started to have motor probs so I borght it in and he put it on the lift and we looked and could see that the frame was a little sideways. Well my qestion is if any of you know how to get the frame stight and what are the mesurments. Thanks to anyone that has a ideas.
~NATHAN~